Device for detecting arterial pressure

ABSTRACT

A device for detecting arterial pressure with high measurement precision, comprising a cuff with inflatable chamber, adapted to be placed around the arm of a patient, elements for introducing air to inflate the cuff, and decompression elements suitable to decompress the inflatable chamber, the device further comprising elements adapted to detect and store all the sphygmic pulses generated by arterial pressure and to identify the pulses that correspond to the appearance and disappearance of the wrist beat, detected by a detection technique that requires the intervention and judgment of an operator.

TECHNICAL FIELD

The present invention relates to a device for detecting arterialpressure. More particularly, the invention relates to a device suitableto detect arterial pressure, generally known as sphygmomanometer, whichis capable of giving maximum objectivity to the measurement made.

BACKGROUND ART

As is known, the sphygmomanometer was introduced at the end of the19^(th) century and is still universally used today according to themeasurement technique perfected in the early 20^(TH) century.

Such instrument, composed of a manometer connected to a chamber that canbe inflated by means of an air-bulb, is designed to oppose a knownpressure to the arterial pressure and therefore allow to read thepressure values when blood flow is detected, by listening with astethoscope during decompression of the cuff that contrasts the knownpressure, and subsequently, by auscultation, the level at which theaction of the cuff no longer affects the detected sounds.

The inflatable chamber, integrated in a cuff that is applied to the armof the patient, produces on the arm a pneumatic pressure that exceedsthe arterial pressure at a certain point of the compression,interrupting the flow of blood downstream of the cuff. Once the arterialpressure has been exceeded by 20-30 mm Hg, decompression of the cuff isperformed by means of a pneumatic valve that is normally integrated inthe bulb.

During decompression, the operator listens to the sounds produced by theartery, detected by means of a stethoscope that is appropriately placedon the arm. In this manner, the operator detects a series of soundshaving mutually different tones, intensities and durations, produced bythe arterial pulses, which in turn are a consequence of cardiac activityand of the resistance of the arterial vessel. At this point, theoperator must determine which of these pulses represents the systolicvalue (maximum pressure) and which one represents the diastolic value(minimum pressure).

The above described measurement of arterial pressure however suffersdrawbacks that are due to the fact that the measurement inherently hasthe following subjective aspects.

Excessively rapid decompression rate: the error due to an excessivelyrapid decompression rate in the cuff derives from the reaction time ofthe operator.

When the operator detects the pulse that determines the systolic valueor the one that determines the diastolic value, he/she reads on thegraduated scale of the manometer the value, which in the meantime hasdecreased as a function of its decompression rate.

As a consequence of this, medical doctrine prescribes a rate between 2and 3 mm Hg per second as regards decompression. However, in practicethis prescription is commonly ignored, because there is a tendency toreduce the time required for the measurement, underestimating the errormade and therefore failing to obtain reliable data.

A second type of error is given by a parallax error, i.e., by anincorrect placement of the operator with respect to the manometer. As isevident, such error can be opposite in sign and variable in meaning,with random characteristics, indeed depending on the position that theoperator assumes with respect to the manometer.

Another error is given by the operator's natural tendency to round offthe read value to a value that is easy to memorize. This rounding off isusually performed to 5 mm Hg and sometimes to 10 mm Hg.

Yet another error is given by the uncertainty in determining which pulseindicates systolic pressure and likewise which pulse indicates diastolicpressure.

In the first case, the phenomenon that causes so-called supermaximalpressure is known in the doctrine. When decompression begins, one waitsto detect the first pulse in the stethoscope. The first pulse normallyindicates the systolic value (maximum pressure). However, the firstpulse does not always correspond to flow of blood beneath the inflatablechamber caused by the blood pressure exceeding the pressure thatcontrasts it by means of the cuff. Actually, with a high-intensity wristpulse it is possible to detect pulses produced by the impact of thearterial pulsation against the edge of the cuff that constitutes theobstacle that cannot be passed until its pressure has dropped below thelevel of the arterial pressure.

Substantially, this noise may be audible with a variable acoustic leveldepending on the intensity of the wrist pulse. In the presence of a“strong” pulsation, these supermaximal pulses must be discriminated bythe operator by comparing their intensity with the subsequent pulses.

In the second case, there is uncertainty in determining which pulse canbe defined as a diastolic pulse, i.e., the pulse that indicates theminimum pressure. Determination of diastolic pressure has always beenmore difficult to define, and uniformity of its results is currentlyunsolved.

Electronic sphygmomanometers are currently known which use the principleof the manual sphygmomanometer but replace auscultation by the operatorwith detection of the signal by means of a microphone or by detectingthe sphygmic pulse in the form of a pneumatic oscillation within thecircuit of the instrument, caused by the arterial pulsation itself.

The first method is the closest possible analogy to stethoscopicauscultation, with the difference of replacing human abilities inhearing and processing the signal with electronic means that can offerdifferent results due to obvious inherent characteristics.

The second technique has greater operating differences, since it is notbased on the same element described above, i.e., the noise generated byblood flow, but on a different element, such as the pneumaticoscillation inside the circuit of the instrument, caused by thepulsation itself. By processing with increasingly sophisticatedalgorithms, an attempt has been made to attain a result that is as closeas possible to the result that can be obtained with human auscultation,but currently it is not possible to have a completely reliablemeasurement.

DISCLOSURE OF THE INVENTION

The aim of the present invention is to provide a device for detectingarterial pressure that substantially allows to improve the precision ofthe measurement.

Within this aim, an object of the present invention is to provide adevice for detecting arterial pressure that allows to eliminate thedrawbacks due to an excessively high decompression rate, to parallaxerror, to the operator's tendency to round off the measured value, andfinally to the uncertainty in determining the pulse to be defined assystolic and the pulse to be defined as diastolic.

A further object of the present invention is to provide a device fordetecting arterial pressure that maintains the central role of humanassessment in pressure measurement, supporting it with the aid ofelectronic means.

A further object of the present invention is to provide a device fordetecting arterial pressure that is highly reliable, relatively simpleto manufacture, and at competitive costs.

This aim and these and other objects that will become better apparenthereinafter are achieved by a device for detecting arterial pressurewith high measurement precision, comprising a cuff with inflatablechamber, adapted to be placed around the arm of a patient; means forintroducing air to inflate said cuff, and decompression means suitableto decompress said inflatable chamber, characterized in that itcomprises means adapted to detect and store all the sphygmic pulsesgenerated by arterial pressure and to identify the pulses thatcorrespond to the appearance and disappearance of the wrist beat,detected by means of a technique for detecting sphygmic pulses generatedby arterial pressure that requires the intervention and judgment of anoperator.

BRIEF DESCRIPTION OF THE DRAWING

Further characteristics and advantages of the invention will becomebetter apparent from the description of a preferred but not exclusiveembodiment of the device according to the present invention, illustratedby way of non-limiting example in the accompanying drawing, wherein theonly figure is a block diagram of the apparatus according to the presentinvention.

WAYS OF CARRYING OUT THE INVENTION

With reference to the figure, the device according to the presentinvention, generally designated by the reference numeral 1, comprisesair pumping means 2, for example of the manual or electric type, whichare connected to a cuff 3, inside which an inflatable chamber isaccommodated. Decompression means 4, conveniently constituted by acompression valve, are adapted to perform a constant and controlleddecompression of the cuff 3, as prescribed by medical doctrine toperform an accurate measurement.

The device further comprises means 5 for complete and instantaneousventing of the air of the cuff 3. The venting means 5 are constituted,for example, by a valve that allows to discharge instantly, at theoperator's choice, the air from the cuff 3. As an alternative, it ispossible to use as a vent the same decompression valve, usedappropriately.

The device according to the invention further has pressure transducermeans 6, which are adapted to detect electronically all the sphygmicpulses generated by arterial pulsation and are connected to storagemeans 7 adapted to store said pulses. The means 6 for detecting thesphygmic pulses further allow to identify the pulses that correspond tothe appearance and disappearance of the pulse, detected by means of anydetection method that provides for the intervention of the operator andfor his subjective judgment.

The transducer means continuously detect the value of the pressure ofthe cuff, like a normal manometer does. This value is reported in realtime by the display and recorded together with the detection of thesphygmic pulses. Accordingly, once the measurement has ended, theoperator can analyze, on the display, a listing in which, next to thepressure values expressed for example in mm Hg (or KPa), he/she canread, at the pressure pulses, a value that indicates their sphygmicintensity.

The operator, when he perceives the stethoscope pulses (or pulsesdetected in another manner) that correspond to the systolic anddiastolic pressure, presses a button of the device to “mark” thesevalues on the digital scale of the device.

Substantially, therefore, the user performs a manual detection of thepulses by means of the conventional stethoscope (or, as mentioned, bymeans of any other method), but the means 6 for detecting sphygmicpulses are associated with said detection and allow to identify thepulses that correspond to systolic pressure and to diastolic pressure.

Storage of the data, i.e., of the pulses and therefore of the chart,allows to determine with certainty the pulses that actually correspondto the maximum and minimum values of arterial pressure, performing thisanalysis after detection by means of the stethoscope.

Substantially, therefore, the operator has control over the measurementsperformed manually, and accordingly can associate the precision ofmanual detection with a device that allows to eliminate the previouslymentioned uncertainties that are inherent in the measurement.

The device is further provided with display means 8, which are adaptedto display at least the following detected pressure levels: in realtime, at the stored times, with previous measurements (i.e., measurementhistory).

The device according to the present invention is capable of transferringthe detected results to other storage and/or printout means.

It should be noted that the measurement method currently in use, i.e.,with a cuff provided with an inflatable chamber, prescribes the use ofan inflatable chamber that is proportionate to the size of the arm ofthe patient. However, since in practice it is not possible to have acuff for each patient, medical doctrine has established three types ofcuffs for three different types of patient. However, very often anoperator does not comply with these indicators and always uses a singlestandard cuff.

The use of a standard cuff, however, is another source of error, whichadds to the previously described errors that are inherent in themeasurement.

For this purpose, the device according to the present invention uses acuff 3 on which a scale is printed along its entire longitudinal side,said scale indicating, when the cuff is applied, the circumference ofthe arm of the user. This information can be used, by entering it in thedevice according to the invention, as a corrective factor for thearterial pressure measurement that is made, accordingly complying withthe criteria of using a cuff for each type of patient.

In practice it has been found that the device according to the presentinvention allows to perform a manual measurement with a stethoscope ofthe arterial pressure of a patient, with the association of meansadapted to detect the sphygmic pulses generated by arterial pressure andto then identify the pulses that correspond to the appearance anddisappearance of the pulse detected by means of the stethoscopictechnique. These pulses correspond respectively to systolic pressure andto diastolic pressure.

The operator, therefore, can perform a manual measurement with the aidof a sort of electronic measurement for control and confirmation. Thedevice according to the invention allows to store the chart of thepulses in order to perform a subsequent verification thereof, so as todetermine assuredly the pulses that actually correspond to the maximumand minimum values of the arterial pressure.

The device thus conceived is susceptible of numerous modifications andvariations, within the scope of the appended claims. All the details maybe replaced with other technically equivalent elements.

In practice, the materials used, as well as the contingent shapes anddimensions, may be any according to requirements and to the state of theart.

The disclosures in Italian Patent Application No. MI2003A001683 fromwhich this application claims priority are incorporated herein byreference.

1-10. (canceled)
 11. A device for detecting arterial pressure with highmeasurement precision, comprising a cuff with inflatable chamber,adapted to be placed around the arm of a patient, means for introducingair to inflate said cuff, and decompression means adapted to decompresssaid inflatable chamber, further comprising means adapted to detect andstore all the sphygmic pulses generated by the arterial pulsation and toidentify the pulses that correspond to appearance and disappearance ofwrist beat, detected by means of a technique for detecting sphygmicpulses generated by arterial pressure that provides for the interventionand subjective judgment of an operator.
 12. The device of claim 11,wherein said decompression means of said inflatable chamber comprise avalve for providing constant and time-controlled decompression.
 13. Thedevice of claim 11, comprising discharge means adapted to completely andinstantaneously discharge the inflatable chamber of said cuff.
 14. Thedevice of claim 11, wherein said means for detecting and storing thesphygmic pulses are connected to data storage means, which are adaptedto store the chart of the sphygmic pulses.
 15. The device of claim 11,comprising a display that is adapted to display detected levels ofpressure and levels of sphygmic intensity of the pulsations.
 16. Thedevice of claim 11, comprising a button that is adapted to be pressed bythe operator when the operator detects sphygmic pulses that correspondto systolic or diastolic pressure.
 17. A method for detecting arterialpressure, comprising the steps of: pumping air into a cuff provided withan inflatable chamber; decompressing said inflatable chamber; detecting,by means of the intervention and subjective judgment of an operator, thesphygmic pulses that correspond respectively to the appearance anddisappearance of the wrist beat, further comprising the steps of:detecting and storing all the sphygmic pulses generated by arterialpulsation by using an electronic sensing and storage circuit;identifying, among said sphygmic pulses, the ones that correspond to theappearance and disappearance of the pulse beat, detected by means ofsaid stethoscope.
 18. The method of claim 17, wherein said step ofperforming the decompression of said inflatable chamber comprisesperforming decompression at a controlled and constant rate.
 19. Themethod of claim 17, further comprising a step of storing said sphygmicpulses generated by arterial pulsation, in order to allow subsequentanalysis of the chart of sphygmic pulses, in order to determineassuredly the pulses that actually correspond to the maximum and minimumvalues of arterial pressure.
 20. The method of claim 17, comprising astep of pressing, on the part of said operator, a button when sphygmicpulses that correspond to systolic and diastolic pressure are detected,said sphygmic pulses that correspond to systolic and diastolic pressurebeing “marked” on a digital scale of said device.